The present invention relates to television (TV) anti-copy protection (ACP) processes as well as to processes for defeating or reducing the effects of copy protection signals and, more particularly, to various unconventional techniques for identifying the occurrence of the vertical blanking interval (VBI) in a television signal. This information is required in copy protection defeating processes which need to locate the VBI in order to remove any of the various types of copy protection signals that conventionally are inserted in various video lines in the VBI. The invention further relates to techniques for defeating the processes of identifying the VBI, that is, for preventing the identification of the VBI via the unconventional techniques disclosed herein.
In the television field, the development of copy protection processes for protecting television signals recorded on various recording mediums or transmitted over various transmission mediums, has resulted in the proliferation of schemes and devices for locating and then removing the copy protection signals from the TV signals in order to illegally copy the recorded or transmitted signal for profit. Typical of such devices for defeating copy protection processes are those known colloquially as “black boxes.”
Various types of illegal black boxes are effective in neutralizing respective types of copy protection (or scrambled) signals such as those using for example, pseudo sync/AGC pulse manipulation, horizontal or vertical sync suppression and/or modulation, color burst manipulation, etc., techniques. In most such types of illegal black boxes it first is necessary to locate a reliable vertical sync or vertical rate signal. Once a reliable vertical related signal is established, circuits such as sync separators and low pass filters deliver timing signals which in turn enables the defeat of the copy protection signals and the generation of a viewable video signal. In a typical technique, circuits are used to identify the characteristically longer broad vertical sync pulses to generate a vertical (or frame) rate signal. In a further technique, black boxes utilize the color burst signal in the television signal to attain illegal decoding, wherein the lack of color burst in conventional lines of the VBI can be detected to thereby identify the VBI and enable the illegal generation of a reliable vertical rate signal.
In a still further type of black box technique, a computer is used to analyze a video signal to determine the location of the VBI and generation of a vertical related signal, thereby enabling the illegal decoding of the copy protection signal.